You're fine. Don't sweat it. If you'd like to shoot slugs, shoot one designed for smooth bores. A Brenneke or what they call a "rifled slug" will do fine. Slugs shoot best from Cylinder or Improved cylinder guns but are safe to shoot through full-choke barrels.
On the barrel of your shotgun, close to the receiver you will see the choke listed something like this:
CYL = Cylinder bore, no constriction.
IMP = Improved Cylinder, slight constriction.
MOD = Modified Cylinder, medium constriction.
FULL = Full Choke, tight constriction.
The tighter the constriction, the bigger your pattern at any given range. If you're shooting skeet or stuff up close, you'd do better with less constriction. Also good for slugs. What's your gun?