Sore nipples 2 year old son

I still breastfeed my 2 year old son.. yesterday, I had some brown discharge & very very sore nipples since. I am on the mini pill- I do not get my period on it. My s.o. and I are sexually active. On December 12, I accidentally missed a pill for the first time in 2 years dealing with a very sick baby who has RSV & refused to sleep. I ended up falling asleep in the rocking chair with him (I take the pill at 10pm after I put him to bed every night). I didn’t realize I missed it until I went to take it the following night. Whoops. We did have sex 3 days prior to me missing the pill. It is very painful to breastfeed & when my son plays with my nipples, I cringe.. is this a normal thing that happens with a 2 year old or is this related to me missing the pill? I haven’t missed a day since.