I ran the tough mudder sat & have several scrapes and sml cuts on knees. got a tetanus shot this am, should i be okay? last booster less than 10 yrs.

Yes: From tetanus, anyway. Make sure you clean the "mudder" out of the cuts / scrapes and watch for increasing reddness, suggesting infection and need for antibiotic topically (and maybe orally also).

Tetanus coverage ok: You should be ok as far as tetanus is concerned, but look out for other infections as for example your hair follicles.

Yes: If you have booster w/;in 10 years you should be ok with tetanus shot. Keep your cuts and scrapes clean and watch for any possible skin infection.