Hi Sophie,
First of all, don't be embarrassed. Doctors are used to seeing all kinds of problems. When it comes to lumps and bumps and all kinds of issues with our bodies, most doctors have seen it all.
Most breasts lumps are benign (caused by something other than cancer) but it is always a good idea to have them checked out. An inverted nipple can sometimes be a sign of trouble as well. Do make an appointment with your doctor. Most likely you will find out that nothing is wrong but being reassured is also a good reason to get checked out.
Take good care,
Laurie