abs light on after brake job

I have a 03 tracker 4wd 2.5l engine.
I just changed the rotor, pads, pins, pin boots, and caliper bracket, on the
drivers' side, one of the pins locked up and trashed the pad.
Passenger side looks practically new so I did nothing to it.

The mechanics look good, and the brakes work.

But going down the road the abs light comes on.
It does not come on when the tracker is not moving.

Research tells me it must have something to do with a speed sensor?
Or maybe I need to change the other side also?

Just seems odd, the abs light has never come on before.
I am not a mechanic, I did the job myself with information from youtube, and
I'm poor :p.