Hello, I have a very physically demanding job, and this morning at work I suddenly felt a "bruise" pain underneath my right armpit. I ignored it, but it got worse and worse during the day, and now its swollen and really hurts.
I bought some Deep heat cream for muscle pain, but can I use it in my arm pit, or is it too sensitive of an area? I'm also gonna take some Diclofenak I have lying around.

Appreciate help and advice. Thanks!