He moved north at the first opportunity. Way north. He cut all ties, even to his mother, which was the hardest on him. He was a mama's boy.
His hair went white from all the stress, including his beard. He took that as a sign to change his appearance and began dressing in pants as soon as they were invented. All the sedentary hiding made him gain tremendous weight, face filling out, giving him rosy cheeks in the snowy environment.
He stayed in doors as much as possible, but always came out around his birthday. It was too lonely, even with the elves that had found him and made camps all around his house. They fashioned him thick, orthopedic boots and gloves that comforted his scarred extremities. It allowed him to take up carpentry again.
The gregarious wee folk did so much for his spirits that he reached out to a similar-sized people: children. He still only went south around his birthday, but brought a sack of the toys from his workshop for those boys and girls who had the right attitude. There were always more gifts to give, too, as the elves copied his work and began production for every decent child.
And associating with children turned out to actually help, for in his old life he had been an average-sized Jew, but to them he was a giant. So his new identity was a jolly mammoth with a white beard and a bag of presents. He was safe. No one down there ever guessed that Santa Claus was an alias.