Chiming in late here...I was diagnosed with fibrocystic breast disease about 11 years ago (fancy name for benign, lumpy, tender breasts...). I was told to cut back on caffeine and chocolate (no way
) The past year or so I've noticed increasing discomfort in the week-10 days before my period. My doc says this is normal - and probably increasing due to hormonal changes related to my age (approaching perimenopause) or chocolate binges 
2 months ago I had a tender spot worse than any other - I called and they said if it still hurt after my period to call back and be seen - otherwise it was a run-of-the mill cyst reponding to hormonal changes. Sure enough it went away in a few days. Some of the info I was given when I was first diagnosed as far as when to be concerned and when not to be....
If it is tender/painful it is likely a cyst - if the pain does not resolve after a cycle have it checked out...
If you have a "matching" lump on the other side it is also likely nothing significant....
If it feels like a small water balloon, and you can move it, it is likely a cyst.
I make sure to do BSE every month so I know which lumps have been there awhile VS. something that is new...this is one of those cases where it helps to be small-busted - I can feel my ribs when I do the exam
Like my (small busted) doc at the time said "hey - if you are looking for a needle in a haystack, it helps to have a small haystack!
My gut feeling is you are fine - but it's always good to check things out!
Mary
Seriously, I have found it is much better to be blunt in most situations ! No beating around the bush here !