Cedric deepened his kiss. He felt like he needed to mark her as soon as possible, if not she might run away. Feeling too desperate for her, his actions turned aggressive. He didn't notice whether she was suffering or not. He just wanted to let her know his need, aggression, desperation, and everything which he feels for her.
Eleanor felt like she was going to be choked by his kiss. She started wriggling but to no avail. He just increased the aggression in his actions. Cedric and Eleanor noticed a coppery taste in their mouths. Only then did Cedric let her be. If not for the taste of blood, Cedric would have continued it.
Eleanor tried to run away, but he held her tight and trapped her between his arms. Eleanor tried to go back, but she couldn't due to the presence of the wall, realizing that she had no way to escape, so she shrunk back as much as possible.