Just before I found out I was expecting my first baby, I found a lump on the side of my Breast. After having a mammograme it was found to be just a clump of fatty tissue and nothing to worry about.. I put it down to early pregnancy to be honest as I haven't felt the lump since having my daughter who is 6 now.. Definitely get it checked but don't worry yourself too much :)
Get it checked but it can be pretty normal to grow extra tissue, moles and skin tags in pregnancy due to hormones. I grew a weird tiny 'mole' shaped bump on my nipple in my first pregnancy. Same colour as my nipple, just next to where a stream of milk comes out. Also grew about a 100 extra tiny freckles/moles on my stomach and chest area. They are tiny so not very noticeable, but my hormones must have been a pretty out of balance!