1. Contact the journal editor: First of all, you should contact the journal editor immediately and tell them your findings. They may ask you for more detailed information, or they may conduct their own investigation.
2. Recheck the data: When communicating with the journal editor, you should recheck your data. Make sure that you have not made any mistakes, or that your mistakes have not been misunderstood.
3. Update your paper: Once you determine that there is something wrong with the data, you should update your paper and point it out where appropriate. This may include adding new tables or charts, or providing more explanations in the conclusion of the paper.
4. Apologize to the readers: If your data problems affect the conclusion of your paper, you should apologize to the readers. Please explain how you found this problem and what measures you took to solve it.
5. Consider withdrawing your paper: In some cases, you may need to withdraw your paper. For example, if your data problem is serious enough to mislead readers, or a journal asks you to do so. In this case, you should contact the journal editor as soon as possible to understand their policies and procedures.
Remember, the most important thing is honesty and transparency. If you make a mistake, it is the best strategy to admit it and correct it as much as possible.