Write on the front side: ACCEPTED
Flip it over write on the back side on a spot with adequate white space:
WITHOUT RECOURSE
PAY TO THE ORDER OF
NOSTRANAUT (<-Your legal name in all caps)
By: Nostronaut, agent (<-your "living man" first and last name using lower case letters and only first letter captialized)

You just did a special indorsement on the bill pursuant to UCC 3-205, and the bill is a negotiable instrument worth its face value pursuant to UCC 3-104.
Scan the front and back of the bill and save it on your computer.
Now you "negotiate" that indorsed bill by tendering it as payment via USPS certified Mail with a green return receipt to the court or wherever it asks for payments to go on the bill. Scan and save the certified mail receipts and the return receipt once it arrives to you later.
You just paid/performed on the bill in full, and any attempt to sue you for the amount is defendable using UCC 3-603(b) and the evidence you saved as exhibits. Don't be scared because if it is a court receiving your bill they should know it is a lawful payment and your obligation is discharged completely.

Here's an example of the special indorsement
https://image.nostr.build/6a50faf9b924582c77926bc3f231f9eb0dbfef52c7b3d458144505dc650c2bfa.jpg 

 And celebrate your negotiable instrument payment by stacking some sats with your currency instead 

 None of this should be construed as discharging your moral obligation to support your child, mind you. This is just a legal, lawful payment so courts can't put you in prison. 
Keep trying to get in contact with your baby mother and child, and be a part of your child's life and support them, of course. Cheers