As noted in the other answer, the OP had over 160 rep at the time he created the bounty, so a 100 rep bounty was within the rules.
See the FAQ on [Meta Stack Overflow] for more than you ever wanted to know about bounties.
In this case, the bounty expired about 7 hours ago as I write this. The person who created the bounty has a 24 hour grace period to award the bounty; if they don't, the Community user awards 50 % of the bounty according to the rules from the FAQ:
- The answer must have been given after the bounty was started
- The answer must have a score of at least +2
- The answer must not have been written by the bounty starter
It looks like yours was the only answer started after the bounty, and you have the +2 score, so (unless the OP decides on the other answer) you should be seeing the bounty in about 17 hours.
While yours was the only answer started after the bounty, you only had one upvote during the bounty period, so the bounty wasn't awarded.