Late payments on credit report

Does anyone know how to remove an account (self lender) from my credit report? It is reporting 30 days late even though it is paid in full. This is really hurting my credit and I’m in the process of getting a mortgage.

Link to the Consumer Finnancial Protection Bureau on how do I dispute an error on my credit report.

Is it actually an error or was it late once and now it is paid in full?

Late once but now paid in full. It makes me so angry because it’s me that I’m paying back (self lender) and it was only $25 that I just accidentally over looked. Now it has reduced my credit score 39 points.

Many years ago I was late once for a payment. I called the creditor and was able to have the late payment removed from my credit report. No guarantee.