forgot stop the instance

Create a ticket selecting "Account and Billing" using these instructions and ask for it:

https://docs.aws.amazon.com/awssupport/latest/user/case-management.html

I cannot tell you if this will be accepted or not, but this is the process you should follow

Additionally, to avoid this problem in the future, read the "Using the AWS Free Tier" in the AWS Billing User Guide.

The topics "Avoiding unexpected charges after the AWS Free Tier" and "Tracking your AWS Free Tier usage" should be required reading before launching your first instance.