Switching dog food if dog is not currently doing well on new food?

I had to abruptly switch my dog's food because Chewy could not deliver my food on time due to COVID-19. It is not a food I can gt in a pet store and nobody online could get it to me. I got what I thought was a good choice, Nutro Ultra Large Breed Chicken Adult Dry Dog Food, he was formerly on Now Fresh Grain-Free Large Breed Adult, but his poop has turned soft and yellow so I know it is not agreeing with him, plus he is biting and licking his paws a lot, which I believe is due to the food as well. My question now is, how do I transition to a new food? Keep giving him the Nutro even though he is not doing well on it? I also stopped giving it to him the past three feedings and gave him chicken and rice to try to get his digestive system back on track but his poop was harder but still yellow. I don't really want to go back to his old food as he was getting bored with it and I don't like the fact that if I'm running low I have to rely on a shipment instead of running to the store. Just kinda at a loss as what to do. Go back to old food without transitioning? Transition from current to new? Stay on chicken and rice and get new food? Any advice would be greatly appreciated.