Hmmm. So much depends on the rest of the board, both the ko threat situation and the size of other plays.
I think that Black can play when he is not afraid of the ko below, and the rest of the board is hot enough.
How hot is the rest of the board? - is a 3 point sente.
There are a couple of other variations. I like these two.
JoelR: I don't understand the first two lines. Isn't the first diagram gote seki for White? In both lines, I think Black can get life, which would have to be better than the seki.
Bill: No, Joel, life is not necessarily better than seki. As a rule, getting out on the right is worth more than the 5 or 6 points Black gets for life. The diagram does not show what's on the right, so we are guessing. But getting out is typically worth 7 points or more.
As for whether the first diagram is a sente or gote for White, we do not know the size of other plays on the board. However, just looking at this corner, and assuming White territory on the right, capturing the single White stone on the right is worth less than the earlier plays. Again, we are guessing, because the diagram does not show what's out there. But in theory it is White's sente.
Correct play here depends on so many factors that it is hard to say what is right.
Holigor, how did the play go in the game?