This is all your responsibility, and I mean that in a GOOD way.
You need to continue to TRAIN and socialize your GSD so you know he will listen and obey and be comfortable around children. DOG CLASSES!!!
You need to NEVER leave your dog/child alone together or in a situation that your dog will grab your child. Baby gates, crates, the TRAINING I mentioned earlier.
Teaching your child to respect dogs and leave them alone. Both children AND dogs can learn the 'leave it' command. Since you will now be there 100A% of the time to supervise and manage the situation, as the calm leader, there should be more calm.
Was it a bite with stitches? Or more of a grab and hold?
EXERCISE EXERCISE EXERCISE EXERCISE!!! Get your dog out of the house and with miles of running and exercising and playing with dog friends to relieve stress and make Nieko calmer when he's home.
Training. Socialization. Exercise. Managing the situation. Teaching both dog AND child......
And if adding a piglet to your home is too much right now, then it just is. Last in, first out is the rule in my home if there is a situation when adding a new pet. It's not the 'older' pets fault, they didn't ask for the new addition. And if I didn't properly train/socialize/prepare for the new pet then it is MY fault and I deal with it my rehoming the newest addition.