i hit my little brother

hes 2 years old and im 18. i was taking care of him and he got ontop of me to play then he started hitting me with his toys. he found it funny when id tell him to stop and that it hurt so he kept hitting me. it didnt hurt bad because they were lighter objects but then he grabbed another one of his toys that was much heavier and he tried to hit me. i knew he was gonna do it so instead, i hit him first. i wasnt thinking rationally but it doesn’t excuse my actions. i feel really guilty and sad for him. i usually slap his hand or his butt but this time i slapped him on the side of his head. the thing is though, i think i hit him too hard. i realized my hand was tingling and all i could think about was how horrible he must be feeling. he started crying for my mom and i rubbed where i hit him gently. he calmed down and went back to acting as usual. like it never happened. i was really concerned so i googled symptoms for a toddlers concussion and how long it takes to show and so far nothing. i just really hope hes okay.