not sure what "estoi" means in "El unico problema es k no estoi a tu lado"
The sentence should read: El único problema es que no estoy a tu lado.
estoy = I am
The whole sentence = The only problem is that I am not with you (literally, "at your side")
Welcome to the forum.
Hello. It's a misspelling of estoy. It means 'I am'. So the whole sentence is, "The only problem is that I'm not by your side."
estoy means I am though it is usually used for a feeling or something non perminant