No

No, you can't risk upsetting him. You move your head forwards, and open your mouth, offering it to him to place his cock in. And he certainly does so. Initially, he's careful. He let's you move your head up and down his dick, rolling your tongue around it. It taste horrible, and the act is made much much worse by the humiliation factor: this was just in your ass. And it's covered with a residue of cum in addition to your insides. Absolutely gross.

However, eventually, he seems to lose interest in taking this slowly, and grabs the back of your head, forcing you to go down hard on his cock. Over and over again. You almost vomit, but luckily your gag reflex is relatively easy to control. Small blessings, you suppose. He releases his final seed in the back of your throat, and takes his dick out. "Swallow. If I see you spit even a drop of that semen out, you'll regret it." You nod, mouth shut, and swallow as best you can. It tastes foul, but it eventually slips down. "Now get out of my shop."

You quickly get up and leave the backroom, and look in the shop for something to wear. "Hey, didn't I tell you that you needed to go?" You hear him calling from behind you. But can you go out like this? You are wearing no clothes, there's duct tape on your ass, and you're walking funny because you were fucked so hard with an unlubed cock in your virgin asshole.