Do not worry too much about it. Dmm like these are properly designed and can take the sort of abuse.
You can check the diode check by a) in diode check setting, short the leads together, the meter should read 0V, b) get a diode measure the diode in both directions - one direction should read the forward V drop (0.7V) the other direction should read open. If this works, your dmm is ok.