Motor on Mini 2

I been flying my mini 2 today no problem, landed to change the Battery, then ready to fly again but had a problem with the front right side motor tried to start up it the front motor wasn’t turning and it shut down tried again the same happened. So I checked the right side motor and it was stiff and it was grating as though it had some dust in it, tried to blow it out but it was still the same, looking forward for any answers,Pete