Well, I don't think there's tickling in the klingon dictionary...but if my brother still has it maybe i could check, i'm not the person you asked, but oh well
Informal way (used with someone you know well):
Por favor, não faças cócegas nos meus pés!
Formal one (to someone older or who you don´t know that well):
Por favor, não faça cócegas nos meus pés!
For gramatical reason the best way to say it in portuguese would be with "por favor" at the end of it, something like: don´t tickle my feet please!
You need to have in mind that Portuguese from Portugal has slight variations from brazilian Portuguese. Someone from Brasil will tend to take away the plural and so they will say cócega instead of cócegas and no meu pé rather than nos meus pés.