1) Replace the tire. You know, safety on 2 wheels and all that stuff. You got 2/3 expected life out of the tire. That's pretty good.
2) Repair it with a mushroom plug installed from the inside.
3) Tire sealant. Be selective as some cause corrosion to your rims and leave a real mess at tire change time. Ride-on is reputed to be a good product. http://www.ride-on.com/motorcycle-formula-mot.html