My Amstaff, sometimes when showing me affection, will nibble my earlobes in the most delicate manner. It amazes me that a dog with such powerful jaws can be so gentle.
When I first read your post, I puzzled: What's an Amstaff? Is that some exotic breed like a Saluki? Then I figured it out... I first saw a Staffordshire a few years ago at a vets office. I was stunned by how incredibly gorgeous it was--they have such magnificent head lines. They are really cool dogs, and from what I hear, really smart, feisty and loyal.
Talk about gentle? Just watch my toddler playing catch with my rott. This is a dog that accidentally tore the medial meniscus in my knee JUST by bumping into me while walking through a doorway, but my daughter can reach into her mouth and withdraw a tennis ball or knobbly chew bone with no fear. Even funnier, she feeds my dog (hence the recent addition of 15 lbs on her) the smallest bits of food with out getting a single scratch. Ursa's as precise as a surgeon when she just tilts her head up and picks the food from her hand, as delicate as you please.
She saves the mean mouth for squirrels or raccoons or when she's trying to steal Mommy's ultra expensive Nike running socks (right off Mommy's feet...). And her pigs ears.