Is there an association between chronic pain and social rejection?

Yes there is - Chronic pain can be incredibly isolating for that person; nobody can see how much it hurts or really understand how the pain can take over other parts of their lives. When people are in constant pain it can affect things such as study, work or going out. This often has a knock on effect on relationships and can create loneliness.

Yes, to an extent. Sometimes the chronic pain makes it hard to maintain relationships because sometimes you can't participate with them because of the pain. There are people who will understand, especially if you explain it, and those are ultimately the ones that should matter the most. Social rejection is awful, but if you have a few understanding friends, it will be easier to deal with.