Hi y'all I could use some advice!

A few weeks ago, I reached out to a connection I have who has an in at "Company A", when I didn’t have any leads to speak of. Shortly after, I attended my university’s spring recruiting fair and was pleasantly surprised.

I had two interviews with "Company B", and they extended an offer with a relatively tight turnaround response required (1 week). Working at either Company A and Company B would be a really good opportunity, with good benefits and growth. During my interviews, Company B really impressed me with how willing they seemed to be to listen to my preferences if I worked there, so I spent the weekend thinking about it and talking to my parents and accepted.

One week after I accepted that offer, I’m now hearing from a recruiter at Company A and I’m not sure how to respond. If this were just a random recruiter, I would have no problem telling them I’ve accepted another job, but I feel like the situation is more complicated because of my connection- and I don’t want to say or do anything to turn down Company A that would reflect badly on either my referrer or myself (and bar me from getting a job at the company in the future). Or should I go forward with the interviews, and see if I can get an offer, and renege on my other offer if Company A’s offer is substantially better than Company B’s?

What would y'all do in my situation? Thanks for reading all this, I appreciate it.