What did you eat? How much? How quickly did you eat? Was it your first meal of today? It's difficult to answer your question as there's lots of questions underneath it, but a good starting rule for this and other elements in life is; listen to your body…if you can exercise there and then do it, but of you need to rest and digest, then give yourself time. Only you know what is going on inside of you.
I would say it depends on a workout and what your eating. But if you eat a good balance meal then 20 to 40 minutes is fine. If its a unbalanced meal then like an hour