Purple bruise

Hi, 

I’ve noticed a reddish/purple bruise the size of a 50p coin under my breast. It doesn’t hurt but looks rather painful to the naked eye. I’ve tried calling my GP multiple times, but getting through seems to be almost impossible to book a consultation. Is this any cause for concern? Im not sure how long I’ve had it, as I’ve only just noticed it recently when lifting up my breast to shower.