I gotta be honest; technically this is not a question. It's just a sentence with nine words, but because I am a pro I can infer your question. Your question is something like: i got pain after my bf sucks my breast. Is that bad?
The answer: Unless the pain you are experiencing during sexual relations is requested, measured and safe, it should be stopped and at looked into.
It is a fact that men are known to over grab, squeeze, smoosh, push, shove, twist, and suck a titty. We are like toddlers with a new bike: all energy, no skill. Unfortunately boobies don't come with written directions. Luckily though, they come with audible directions -- YOU telling us what feels great, good, bad and painful. Sometimes guys think (i.e porn "teaches us") bad habits when handling breasts.
But any man with an IQ above an Irish Setter should be able to heed your lesson plan and modify their approach. Remember, breast sensitivity varies greatly. One woman's light sucking is another woman's plunger attack. Either way breast play should illicit pleasure not bruising. What he masturbates to on his laptop or what his S&M ex GF liked is not what works for you.
However, if your man's manhandling is not truly to blame, he is attentive and gentle; perhaps a trip to the doctor is worthwhile. No reason to freak out, but just make sure your sensitivity is not symptomatic of something that needs attention.