Bubble under the skin feet.

Two months ago I found that there are some small bubble under my skin feet. It is grow bigger under my skin and it is not bulge out. My surface skin look fine. When I press on it. It hurts. When they are bigger it is more hurt when i walk or stand for long time. They are not all together. I try to use needle into it. but there are no juice come out. I use plaster acid on it. only skin come out but not bubble one. Still there are some new one come too. How can i get it away?