It feels like there is a very restrictive type band of tissue just under my thumb there.

就是那里，感觉就在我拇指下方，有一系列很紧的组织。

It feels like there is a very restricted tight band of tissue just right under my thumb there.

感觉就像我的拇指下方有一圈非常紧的组织带。

" Under my thumb" is not usually used in a positive way;in other words, the person who is under your thumb is considered weak or inferior.

“Under my thumb” 通常不以积极的方式使用；换句话说，在你的拇指之下的人被认为是软弱或低人一等的。