2422 is an offense under chapter 117 of the Title 18. Under 18 USC 3299, there is no limitation period for offenses under ch. 117 involving a minor victim.
If you or someone you know might be affected by 18 U.S.C. 2422(b), see a lawyer as soon as possible. Don't rely just on information from this site.
My answer to your question is based on the facts that you provide in your question. Additional factual details about your situation could change my answer completely. The law in inherently uncertain and always subject to change.