Dropped my phone and it won't turn on. Charging loops on and off.

Hi there,

I dropped my phone with earphones plugged in.

Upon picking it up, no visible damage to the exterior, however, the phone refused to turn on. When I tried plugging in the cable to charge it, the screen displayed:

Battery icon with a lightning bolt (6 to 7 seconds) >> turned off (3 seconds) >> Battery icon with a lightning bolt (6 to 7 seconds) >> turned off (3 seconds) and ad infinitum (kept going like this).

Please help.

Ben.