Should I start working out my upper body while lower recovers? Also what a good personal trainer app?

Basically I been working out like three times. I went to the gym and did some workouts at home with the Nike app. My legs and glutes are killing me. I should work on upper body for a while until my legs are better? In addition to Nike training club which personal trainer app is the best? I was thinking about getting an app called workout: gym personal trainer and workout tracker. It got five stars on the App Store for iPhone users.