HS,
If he's real, real close, a good head butt to the nose can buy you some time( followed of course with a strike to the adams apple and a front kick to the privates
) You can use the head butt is he's facing you, or if he's got you in a bear hug from behind. It usually results it the perp not being able to see clearly for a few seconds cause of the agony in his nose( dont forget the complimentary kick to the ribs, groin, or face while he's down
)
Take care,
01paw