Should I be worried that my eight and half month male baby don't want to put his ankle on the ground?

Maybe. The ankle should not touch the ground. If you are reffering to the fact that you child is still walking his toes at 8 1/2 months, yes i would be concerned & you should consult a doctor.
Normal @ this age. When held upright, a forefoot approach to the support reflex is normal at this age.As they get older this proping response begins to give way to more leg flexing, the kid will begin to become more flat footed. As the begin to get to stand & cruise on furniture their common posture will generally be flat footed, but occasional toe walking can persist for years in normal kids.