Pimple occuring regularly. The pimple.

Hi. From last 8 to 10 months pimple are occurring on body. They are not quantity but comes on single . first time it came on my legs then on face and now on hands. They come in small in size then they grow in bigger size. These pimple comes once in a month. It pains a lot . one of the doctor said it is due to bit of insects and he gave some medicine but it didn't stop there. Some other doctor told that it is due to allergy and gave medicine but then also it it didn't stop. It pains a lot . when ever pimple occurred I pressured it and as a result lot of blood and puss came out of the pimple . some times I feel tired not able to stand for long time. If the gets into touch with something it pains and cannot be controlled. Presently the pimple is on my hand .I am sending the photo of . thank you