I'm 16 years old and around 1 week ago I felt a kind of swelling under my left armpit. There's no lumps or anything like that, so I don't think it's lymph nodes. It just feels swollen and different to the right armpit. It sometimes aches, but nothing bad. I have been suffering from hey fever for just under 2 weeks also. No other problems. I do suffer from anxiety.
Sorry if this is the wrong place, I wasn't sure where else to post it.
Any ideas what this could be? I'd be lying if I said I wasn't worried, because I am. If there's no logical explanation then I'll visit my doctor.
Thank you.