Is taking the money an absolution for the oath, or is an expiation for the oath still required?

If by your oath you intended to threaten your relative to take 500 Riyals from him as compensation for puncturing the ball, then your acceptance of 500 Riyals from him as a gift for another reason does not fulfill the oath.

So, if you did not take the 500 Riyals from him as you intended by your oath, then an expiation for breaking an oath is incumbent upon you.