If you really want to ride your bike, even for a couple of minutes, then go ride your bike. If you currently aren't doing any exercise, then it's better than doing nothing but as others have said, it's not a replacement for what your doctor said.
Also, if you haven't done any exercise, going all-in with 20 to 45 minutes of intense cardio may not be a good idea. Start lightly and make sure you progress.
Start riding your bike for those errands. Then ditch the bike and start walking. Then start jogging.
Do you have any dumbbells or weights at home? Squats and deadlifts can get your heart pumping pretty hard.
Last edited by Daniel4; 06-18-22 at 04:30 PM.