Filling in gaps

I am trying to sculpt a character and I need to fill in a gap in a part of the character. I try using inflate to fill the gap but when I go to smooth it the gap comes back.

Not sure what Inflate is but you need to merge verts where they join the edges you want to close.

Create a new simple object like a cube or sphere that fits into the gap and boolean it into your sculpt object. Then apply the boolean and pop back into sculpt mode to tidy it up.

Instead of using Inflate, try the Fill tool or Clay strips tool/

Can you upload a photo of it?