Girls, can you tell me what it could be? Yesterday I went to the theat…

Girls, can you tell me what it could be? Yesterday I went to the theater (mom and dad were with the baby) Yesterday started to hurt my left breast (in the evening) We still have breastfeeding, I thought maybe because of this The chest was hurting but the pain didn't stop Today mom saw that there is a little redness, now I look at the redness spreading (I will leave in the comments)