You were given probation with the agreement that you pay the fine.

If you don't pay the fine then your probation doesn't likely end until you do and you might have to serve your sentence if you don't complete the probation requirement.

I strongly suggest that you visit the courthouse and disclose that you don't have the money and want to make some kind of payment arrangement that'll keep you out of jail.

Fail to do that and you just might find yourself arrested at the most inconvenient time.

This obligation doesn't go away.