A pinging noise from the wheels can be due to a broken spoke, or a wheel in need of an adjustment, or a “wheel true” as it’s called.
If you’re interested in a DIY repair, check out the following article on how to true a wheel:
If you’re not a DIY’er, it’s time for a trip to your local bike shop for this issue. You can either bring the entire bicycle, or remove the affected wheel and bring just the wheel. They will adjust and repair as necessary.