Re: How to Avoid Nicknames?
If you say that she’s a close and good friend, then you should talk to her about it. Tell her that while your understand that the nickname she has given your son is out of love and affection…you would prefer that people (don’t say SHE…use the broad word, “people”) call him by his his real name.
I’ve seen little kids try to pronounce their real names and they end up butchering it, lol. It’s funny and cute. My niece Khadija used to go around telling people her name was Jeeja, for example. But Kids do learn their real names. They don’t become confused for life and go around telling people, “My name is Pinky/Bubbly/Munna/Golu-Molu.” 
Like many things…the parents have to use repetition to teach their kids.
Also, while your friend might back off from calling your son by a nick name…that doesn’t mean you’ll always be able to stop it from happening. Talk to your friend about it…if she doesn’t back off…I don’t think it’s something to end the friendship over and it’s not such a huge deal.
Maybe when you’re in a gathering…and the other women call him by the nick…tell them “Oh I want him to learn how to say his real name…and I’d appreciate it if you all (apart from my husband and I) would also help us out by referring to him as his name.”