Please send us photos of the whole tree, around the base of the tree, and the hole in the trunk so we can see what you may be dealing with.
This does not look like root rot. This looks like an old wound and is trying to heal. No pruning paint is required. Prune off the suckers that are growing around the base of the trunk.
You did not mention what the canopy of the tree looks like such as branch dieback, poor growth, etc. If the tree is putting out new growth and is healthy, improve growing conditions. You can increase the mulch area out to the dripline of the tree. This will prevent lawn mower damage and help keep the weeds down. Make sure mulch is no thicker than several inches and away from the base of the trunk. Water during dry periods.
Thank you Marian
You are welcome.