Snape illuminated the tip of his wand with a flick, and said, "Open your collar," before acting as if Harry didn’t exist, and as if he was merely peering at an interesting crack in the castle walls, rather than at a human being. If he was honest, Harry couldn’t blame him - he didn’t particularly enjoy having to be in such close proximity with the potions master either, and he tried his best to ignore how uncomfortable he felt. If Snape was satisfied, or dissatisfied, with the progress of Harry’s healing, he kept it close to his chest until he was finally ready to speak.