There is still some debate about when it is safe to return to contact sports but the biggest risk for a ruptured spleen is in the first 3 to 7 weeks of illness.

https://www.texaschildrens.org/content/wellness/splenic-ruptures-what-athletes-need-know#:~:text=There%20is%20still%20some%20debate,with%20mononucleosis%20have%20this%20complication.