Recently, Ive got some fingernail marks on my 3DS analog stick made by my friend and I want a replacement but seems that theres no rubber part replacement just the lower part of the analog stick, so I want to ask if theres really any analog stick rubber part replacement and should I ship it to Nintendo, and where is Nintendo in Hong Kong, Thank you.

Hi, welcome to NintendoLife.
There is a thread for this on the main 3DS thread.
As for where to ship your system, I would call Nintendo/email them. Go to www.nintendo.com for more info.

Didn't you already make a thread about this?

You sound like a Nintendo employee making that generic repair reply. xD

Yes. yes he did.

yea I know I made a thread about this but seems no new reply and I really want to have some more suggestions about this,

There are no suggestions to be made. Contact Nintendo customer service in your country, they will tell you to send in your 3ds for repair. The end.

Your only alternative is to just live with a minor cosmetic issue.

If no one replys to your thread you already made chances are their isnt any new info to be added. If you have addition questions to ask you should ask in your already made thread which is here, http://www.nintendolife.com/forums/3ds/how_do_i_remove_finger... rather than making a new one.

And sorry to say, You being in HK will probably mean you can't repair it. Unless you take it to Foxconn or something, I think you may have to send it overseas to NA, or wherever your system's region is.

I do think that in Japan they sell some circle pad "covers" that will probably cover up the marks while making it comfortable at the same time.

Your best bet would be to try contacting Nintendo proper to set up a repair order, or to see if they can provide you with a replacement somehow. Good luck to you!