The swimming record represents Finny's natural and excellent athleticism, that is combined with his love of sports just for the sheer joy of playing them, not bragging about being good at them. He is a generous, fun-loving person who doesn't need to hold things over other people's heads to be liked. He was well-loved even without bragging about busting a school record. Even though he broke the record without even trying, he told Gene,
"I don't want to do it in public...we aren't going to talk about this. It's just between you and me. Don't say anything about it to anyone."
He states his reason for wanting to do it as, "I just wanted to see if I could do it." As simple as that. He is a curious, active, go-getter, but a humble and likable guy too, and that is what is revealed by the swimming incident.
The tie incident represents Finny's ability to turn every situation into a fun, entertaining, harmless event. The tie infraction was huge, and could have been a big punishment. But, Finny explains it off as a twisted form of patriotism. When he makes the Patch-Withers laugh, he "broke into the charmed, thoughtles grin of a man fulfilled." So, he finds pure enjoyment in making other people laugh and be happy. He does this through the tie, through making up and playing games, and also in not bragging about the swim record. He thrives on being liked and making people laugh.
I hope that those thoughts help a bit; good luck!