I think it's important to use the correct terminology. Did you binge eat (meaning you ate 1,000's of calories ABOVE your calorie range) or did you overeat and stay within your range?
If you stayed within your range then you probably did not gain real weight. The scale might show a higher number, but it will just be temporary.
To gain weight you have to eat 3,500 calories above your range.
It's also better to focus on body fat instead of BMI.