There are few signs that can really be seen.
Your dream, I think, means the following.
I dreamed that I bought a plaster. I may have heard of this kind of thing in reality, so I appeared in my dream.
Plaster is mainly used to treat rheumatism, boils, swelling and pain.
If you dream because you don't feel well, you need a plaster.
Then this reflects that you may have problems in your life recently and hope to solve them.
Twenty dollars, indicating the value paid, is relatively high.
The dream is not detailed enough, such as why you bought it, did you use it? These are also key to dreams. Generally speaking, it's not intense, but it states the solution to the problem.