It seemed like the safest way of playing this game of indulging Master Baggins' dream was to let him lead, let him express what he wanted to do. Considering their difference in size it seemed wise.
At first, it seemed like a good decision. After initial ticklish feeling, Thorin couldn't remember when he was last touched on the places Master Baggins ventured towards, Thorin relaxed and enjoyed the sensation, the touch and the attention.
The trouble began when the little Hobbit focused his attention on Thorin's intimate regions.
The first problem was the urge to just let go and release the tension. It seemed like a rude thing to do since Master Baggins didn't get any kind of attention this far into their encounter.
The second problem was the urge to let go of his inner impulses and just ravishes the small Hobbit losing his bearings and risking inflicting pain where pleasure should be given.
To prevent the first of his problems Thorin moved cutting of Master Baggins' manoeuvring space. That left him on top of Master Baggins, which increased his second problem.
Master Baggins was so small under him that he seemed unable to resist Thorin's advances. That made Thorin feel uneasy. It meant that the both of them depended on Thorin's ability to control himself. He was never too confident in his self-control.
"This is a dangerous game you play little Hobbit," Thorin said as much to warn him of the danger as to sober himself up. "I could break you like a twig."
"I'm not afraid of you," said Master Baggins with passion and conviction. "I will never be afraid of you."
Thorin looked in his determinant eyes in the light of the dying fire. His eyes were calm, his body steady, his arms came up to embrace Thorin and the fear disappeared. At that moment, Thorin didn't fear himself anymore because he knew that he'll comply with anything Master Baggins asks him to do.