Bruno felt terrible about denying their friendship. 

"He had never felt so ashamed in his life; he had never imagined that he could behave so cruelly. He wondered how a boy who thought he was a good person really could act in such a cowardly way towards a friend." (pg 174)

Because he felt so bad about it, it really hurt when he didn't see Schmuel for almost a week.  Bruno was convinced that what he had done was so  bad that Schmuel would never forgive him. However, Schmuel showed up seven days later in their same meeting spot. Bruno apologizes again, but when Schmuel looks up,

"There was a lot of bruising on his face and Bruno grimaced" (pg 174)

Bruno, in his innocence, asks if Schmuel fell off his bicycle because that is the only thing he can relate to that would cause that kind of black and blue mark.  The bruising INFERS that Schmuel was beaten for his actions in the house and for not telling the truth to Lt. Kotler, even though he was totally innocent.  When Bruno tells Schmuel that it looks like it hurts, Schmuel answers,

"I don't feel anything anymore." (pg 175)

Schmuel forgives Bruno and offers his hand in friendship.  It was the first time the boys touched.