hey, i wondered if any1 could help me, or has been in the same situation,

last night i found a lump in my armpit, i feels like the size of a 1p coin maybe smaller and it moves about, i cant feel anything like this on the other side. my mum had a feel and she says its nothing to worry about and she cudent feel anything that shouldnt be there. im petrified its something nasty, im planning on going to the doctors thogh to get checked, im not sure what it could be as i said , the other armpit doesnt match.and also when i move my left arm, sometimes it feels like i can feel the lump move when my arm moves.