One thing you can do is dose up on Vitamin C, Ester C is the best as its the strongest, I have been taking it everyday since bub was born and I got sore breasts when I stopped taking it so I started it up again, most MW's seem to suggest it if you think you are getting Mastitis.
When my left breast was really sore I realised that its the side I hold Heidi on all the time and she likes to squeeze my b@@b between her knees while I hold her

so I started holding her differently and this seem to help too???
Hope it goes away soon!!