Q: I accidentally poured about a cap n a half of oil into my radiator n drove after i tried getting it out, how can it effect my car

I was trying to pour coolant into my radiator because it over heats when sitting for a while but accidentally grabbed the oil. I poured maybe a cap(not cup but cap) and half of oil into my radiator. I tried to get it to come out by pouring what water I had into it because the oil was floating. I was then told it wouldn't effect my car because it was so little so i drove to pick up my daughter and ended up in traffic for a hour n half, so ive been driving. How can this effect my car and what should i do to prevent any further damage.
My car has an automatic transmission.