how long has it been there?
about how big is it?
is it red or warm or painful to touch?
is there redness around it?
is it in the groin? how far down the leg is it?
so my concern with this is the pain.
if it is painful to the touch this may be an abscess..... an infection under the skin. this would not be an uncommon place for one. often they form around hair follicles.
the point is that without seeing it and touching it there is no way to tell you exactly what this is BUT if it is an abscess it is going to get worse and not better and if it is a simple skin infection with bacteria then you need antibiotics.
an abscess needs to be drained, so the best thing for you to do is go to the nearest urgent care or to your physician and get this looked at and maybe drained. delay could be dangerous.
hard to say, but since it's hard to say the ER is the place for you today. the consequence of letting it go are just too risky. someone needs to open it and let the pus out and then you will feel so much better. I would not wait, I am an ER doc. hopefully they can get you in and out relatively quickly.