Around a month ago I found a lump under my armpit when I was in the bath, it was around pea sized…

Around a month ago I found a lump under my armpit when I was in the bath, it was around pea sized maybe slightly bigger. I forgot about it until the other day when I found it again , it was slightly bigger and last night when I was shaving my under arms I must of nicked it a bit and a little bit of puss came out I then made the mistake of squeezing it and blood came out I left it alone after that. I’m guessing it’s just a cyst but is it worth going to the doctor about?