This has more to do with credit

This has more to do with credit rather than debt itself. I have good credit aside from one 300 dollar payment (now paid). I thought it had been paid off a few years back but it turns out about $300 was outstanding.

Not knowing it was and having moved, it is now listed as bad debt on my credit file. My question is does this essentially prevent me from accessing credit until it’s off, or does it just adversely affect my rates for things like mortgages?

I am afraid that I won’t be able to get any credit at all until the 7 yr time frame has passed by and its removed. Any advice or insight would be appreciated.