I Have This Growth Under My Arm Initially I Thought

I have this growth under my arm initially I thought it was a boil but it's been a month and nothing is happening it's just there as it doesn't really look like a boil but right now I feel like that's something traveling down my side to my stomach and I feel a stretch just a line of painful line down my arm going to what's my finger I don't know what's going on could you please tell me what's going on Hi, can I answer your health question? Please type your question here...