There are different types of bearings that are called "sealed".
Old style cup & cone bearings can have a "seal".

Cartridge bearings are another type. More modern applications.
IF that type, you really aren't going to hurt them by riding until they definitely "tell you". they're bad.

The other type needs "normal maintenance". Damage can result to the cone & cup(hub)

What is the brand & model hub?
That may give us the info to Intelligently advise you.