If you two shared IP's for whatever reason you can never interact ever again or you face deletion. Simple as that.
If i were you i would check it was a one off you shared an IP or you face deletion anyway.
Also i'd like to add, while yes the system for detecting multis is more complicated it does not by any stretch mean that its OK to share IP's. The game terms of service clearly state one nation per IP. Accidental one off's are unavoidable on occasion, but don't be under any illusion that its ok to share IP's. Its not.