Dr. Raj Raina, president, CEO, and owner of Medical Associates, based in Hauppauge, has been taking care of patients — and his practice. A primary care doctor who runs the six-site, multispecialty practice, he has kept Medical Associates’ doctors, nurses, and staff busy treating COVID-19 patients as he puts his own pay on pause. And he’s not alone among doctors in private practice on Long Island who are making sacrifices to keep their doors open.