Is it normal that my online friend is acting like this?

Last week we had a bit of an argument and both of us had stressful days so the end result wasn't pretty. I should add we're pretty close so maybe I hurt them a bit too much without realizing it? I apologized a couple of days later after things settled down, and they said it was "fine" and they "got over it". However I talked to that same person a couple days after, and things weren't the same. They'd just reply back with minimal words and said they weren't sure if they were mad at me, which made it clear to me that things weren't fine, and they still dislike me, or they weren't in the mood to talk.

It's been a few days since and I tried reaching out again, to no reply, yet. The thing is I don't get into too many arguments with friends, so I don't know if this is a normal reaction or if they're over-reacting.