Bugs after deployment to production are a fact of life. No matter how hard the piece of software is tested something you never even dreamed about will come along and cause something to fail. If you don't have a (good) QA team testing your code, and automated testing setup, the amount of bugs after deployment could be rather large. Developers by and large tend to fall into the habit of testing the so-called "Happy Path" in their code while writing it. They forget to go back through the other paths.
What would raise red flags is if the bugs people are finding bugs in core business rules. For example, if you created a web form that allowed people to enter their email address but no syntax validation was being performed on it. Or, all users must have an email address, but you don't require it in the form. Another red flag would be if the bugs caused security issues, such as direct injection of SQL into your code.
But if the bugs only happened if you had to follow some insane set of steps such as, the user put their cursor on the test box, held down the space key for 10 seconds, hit tab six times and then clicked a drop down list and exception would occur then I wouldn't stress about it too much.
The fact of the matter is, the module went live and there are bugs in it, you can't change that. After getting them fixed, I would focus on preventing these bugs from ever happening again. If you or your team doesn't have automated testing (both unit and integrated) then I would take a real hard look at it. Because automated testing does what developers tend to forget to do, regression test, as well as test new features. I've mentioned this book before in previous posts, but I will mention it again, the book The Art Of Unit Testing will give you a good foundation. Automated testing will not be a cure-all for this problem. But well written tests should reduce the number of found bugs.
Finally, hopefully you have a QA team testing your code, if you do then I would have a postmortem with them to talk about how the two of you can work better to finding these bugs before deployment. Maybe you can provide them with some queries, or write a little test app to test the load of the system.