Parent Visa For the UK

Your child will be eligible for a uk citizenship by decent therefore he will be entitled to a UK passport, Your child’s father can do this application but you will need to have the child’s birth certificate with the fathers name on it (not an absolute need but makes it a lot easier) you will need marriage certificate and divorce certificate (again not an absolute need) if none of these can be provided you’ll need your child and father to have a DNA test at a centre endorsed by the UK (many around the world)
Once your child has passport your visa application will be a general visit one and all but a formality, you will also need the usual letter of invitation (loi) bank statements etc and from who has invited you to the uk

Thank you so much. And do you know if I will be able to apply for a return visa as I had leave to remain in the past?

I would imagine if you meet the criteria for a Visa application and for your child’s and fathers benefit you should be fine uk immigration/ Visa control do take in to account for broken families, you may have to also prove you’ll leave the uk ie your job or other commitments etc