Are there separate blowers for each side? If so, I'd say one of them (drivers side) is out. Check the fuses before checking the blower.
If not, you have a blockage. Either something has gotten in there or the door controlling air flow to that side is stuck or the actuator (mechanical in this case) has broken free and isn't operating it.
If not, you have a blockage. Either something has gotten in there or the door controlling air flow to that side is stuck or the actuator (mechanical in this case) has broken free and isn't operating it.