[It really must be his lucky day—not only did he find a cute girl, but also said cute girl bumped right into him. Yes, definitely a lucky day. However, instead of just standing here and contemplating how fortunate he is, he should just respond...which he eventually does, of course, but before that happens Sigma just stares at her, making the situation way more awkward than it was, probably.]

N-No, I'm the one who should be sorry! I'm fine, really...what about you, though? I'm pretty sturdy, I hope you didn't get hurt or anything...I'm sure that your patients would kill me if something happened to you.

[His attempt at a joke...well, there was an attempt, at least?]