Simon Cowell’s road to recovery began shortly after he had back surgery earlier this year following a bike accident.“Simon has been up and walking since day two [of being home],” a source exclusively tells Us Weekly.The America’s Got Talent judge, who was hospitalized in August after a fall off an electric bicycle in Malibu that broke his back, has been switching up his physical therapy activities in order to get back to full mobility.“Simon’s having little or no visitors due to COVID, but he’s