Do all breast lumps need to be investigated?

Hi, 

I'm 24 and recently found a small (1.5-2cm) hard lump in my breast about 1 inch above the nipple, it was not there last month. I booked a GP appointment and she poked the lump for about 15 seconds and then said she could tell it wasn't anything sinister just by feeling it and to just come back if anything changes. I'm concerned because she didn't ask me about any other breast things like discharge or pain or discuss family history or anything like that at all. She asked me nothing other than where the lump was. I'm just feeling a bit concerned because I did have some changes in discharge recently on the side with the lump. I don't know whether to just monitor it myself like the GP said or ask another gp to have a look. Any advice!