Dents in above ground pool walls can definitely be concerning, especially when you first notice them. If it’s not leaking and the structure feels solid no bulging or unusual sounds when the pool is full, you’re probably okay to leave it for now and just keep an eye on it.
That said, if the dent is sharp or creased, it could create a weak point over time, especially if it's in a high-pressure area or gets direct sun a lot. In those cases, I’d consider smoothing it out next time the pool is drained. Some people have had success pushing the dent out from the inside with a rubber mallet or block of wood, but you want to be super gentle so you don’t damage the liner or cause more stress.
Also, check the area around the dent for any small cracks or signs of rust if it's a metal wall, those are worth addressing sooner rather than later.