How do I fix my rear axle? Bike was working fine. I was stopped at a stop sign, when I went to pedal it jerked and felt like my chain popped off, but it had not. Pedaling does nothing. The back wheel still rolls if I push it. It’s not locked up and the pedals and sprockets spin but rough now, and it makes a clanking noise. sounds like its coming from inside the axle - I can still use the brakes though. it’s a single speed beach cruiser with coaster brakes.
Most likely the freewheel mechanism in the hub has broken. 

Unless you have the knowledge and tools to disassemble the hub you’ll
have to take the bike to a local bike store or mechanic. 

If fixing the freewheel is not possible replacement of the whole rear wheel is likely the solution as replacing a hub requires rebuilding the wheel which has a substantial cost.