So... I've created a creature in my world that felt somewhat original at the time. I like the creature and it does play an import role in progressing the characters further. However I connected the dots about a week ago for where the inspiration came from and I fear it would be obvious to my readers. Think the Sandworms from Dune mixed with the Graboids from Tremors. Very similar creatures to start with but with notable differences. Would I encounter and legal issues from the creators of either of these? Would people call me out for "being to similar"? I wasn't worried about it until I started rereading Dune, now it makes me a little nervous. I'm sure it's been covered before but I couldn't find it anywhere, probably searching to specifically.
I find that usually when it comes to things I create during a fit of intense inspiration, they tend to become less and less like whatever it is I was inspired by as I hash out the details. I find it also helps to take a concept I'm inspired by and just try visually redesigning it. I'll draw up a few concepts in an attempt to remove it from whatever book or movie or song I was inspired by to begin with and make it feel more like it belongs in my world. I don't think you'll have any legal troubles because of similarities but people may call you out on it if its really obvious. People may also just like your Sandworms more. I think a decent example are the movies "Kill Bill" and "Lady Snowblood". They're pretty similar, personally I'll take "Lady Snowblood" over "Kill Bill" every time but there are many who would beg to differ.
Awhile back, I read this really good article by Holly Lisle about "stealing" ideas. Basically she says "take the thing you want, boil it down to its essence, then play with it - turn it around, shave off the edges, add your own twist to it, and make it your own". Terry Goodkind did with his Sword of Truth series - it's pretty obviously a ripoff of the Wheel of Time, but the books were still bestsellers. As long as you don't outright plagiarize, the end result is what really matters - are your creatures interesting enough that they can stand on their own, whether or not they're obviously derived from something else? If you don't think so, then how can you spice them up so they will be?
I definitely agree on keeping your creations organic. Don't let them stagnate and become one definite thing that you are unwilling to compromise on. Continue to consume art, media, etc., and use what you learn from those to infuse your creation with peculiar, fascinating qualities in a clever and thoughtful way.
As mentioned by most of those above, it's already a trope, not a thing that belongs to just one or two stories. Just don't have these worms poop out mind altering drugs that allow people to fold space, see the future, and have contact with their antecedents and you'll be fine.
It's unusual that I wouldn't know where my inspiration came from when it's this similar to something else. I usually know the moment the idea comes to me exactly where I got it from - it's actually what blocks me from most of my ideas Anyway, I don't think anyone has a monopoly on sandworms - that'd be like saying can I be sued because I've got elves in my book, or worse, Tolkien-esque elves! Nah, you're fine. And if you're not, a forum is not the best place to ask Ask a literary lawyer!
World of Warcraft has sandworms, too. I think by now they're like having goblins or wyverns - no one will think you're copying a specific work.