I just injected 600000 units of penicillin g procaine but i forgot to draw back on the syringe to check for blood vessel. wat should i do?

Good follow up: Accidental administration into an artery or nerve can cause severe neurovascular damage. Serious complications of suspected intravascular administration include immediate pallor, mottling, or cyanosis of the extremity, both distal and proximal to the injection site, followed by bleb formation. I would instruct patient to call if any concerning symptoms (pain, swelling, skin changes, numbness).

Probably nothing: You should check for side effects or complications. If none are detectable there is nothing further to do. If a small say 23 needle was used probably no harm was done. Be more careful next time.

Nothing anymore: Once it's injected, nothing much more to do. The effects of an intravadcular injection are seen within minutes if not seconds. If you don't see those effects shortly after injecting, it's probably safe to assume you did not inject into a vessel.