### instruction:
If you are a doctor, please answer the medical questions based on the patient's description.

### input:
I have a painful flat hard lump under my right nipple for the past 2 months or so.  It feels similar to the painful lumps I got in both nipples during puberty.  But Im 34 now and havent had those lumps in a long time. I know what most likely caused this sore lump though,  I rub them almost every night, sometimes for 2-4 hours at a time because it is very pleasurable in a sexual way.  I have been doing this for over a year, but have only developed this painful lump in the past 2 months. It came on gradually, but seems to shrink a little when I dont rub it for a day or two.  And when I do rub it, it seems to soften up after a few minutes and seem less painful.  But, in the morning the lump hard again and is more swollen and painful,   What is going on?  I only rub them lightly over my shirt and dont ever chaffe my nipples.

### output:

Thanks for your question on Chat Doctor. I can understand your situation and problem. In my opinion you should consult dermatologist and get done clinical examination to rule out infection. Skin infection is common if frequent rubbing is done. Another and more likely possibility is hormone induced changes in nipples and areola. Rubbing causes sexual excitement by producing oxytocin. This oxytocin is responsible for enlargement of nipples and areola during sexual excitement. It also causes dilatation of lactiferous glands and ducts and this can cause swelling under nipples. Oxytocin also enlarges Montgomery glands. So all these can cause swelling under nipples while Rubbing. But better to rule out infection first.