I'm 20 years old now and have had a lump under my left nipple since I was 12. I have never had it looked at. It has in the past 2 years been fluctuating in size and tenderness. I haven't really paid it any mind because it never caused me any issue.

Is it urgent I get this looked at or will I continue to be fine waiting as it is a lump that simply hasn't left since early puberty?