The Pankiti under discussionis:
ਗਿਆਨ ਖੰਡ ਕਾ ਆਖਹੁ ਕਰਮੁ ॥Notice that the verb is spelled as ਆਖਹੁ and not as ਆਖਉ which means that this verb is not of first person; hence there should be no Bindi in the end.
It seems like Guru Sahib is addressing Himself and saying "Now say the Karam of Gyaan Khand". If there had been ਆਖਉ instead of ਆਖਹੁ , then the meaning would have been "Now I am saying the Karam of Gyaan Khand".
The scholar you have mentioned, may have been a student of Professor Sahib Singh but he is not following Professor Sahib Singh jee's translation of this Pankiti. Professor Sahib has translated this Pankiti as, "Now understand the Karam of Gyaan Khand". This way too, there can be no nasal sound at the end of ਆਖਹੁ.
Gurbani is Agam Agaadh Bodh.
Kulbir Singh
ਸਤਿਗੁਰਬਚਨਕਮਾਵਣੇਸਚਾਏਹੁਵੀਚਾਰੁ॥