When can i apply for SSN after/bef Oct1st

Hi ,Now i am in USA on H4.I have valid H1-B from Oct1st,2013.My H4 visa got expired on 27th Sep 2013.When can i apply for SSN.Is there any problem for 3days extension for applying SSN. Thanks,Shiva

You can apply for SSN after Oct 1 when your status has changed to H-1 in their system. Do not apply until then. Your H-1 has been approved w/ COS, correct?

Thanks Saurabh, H1-B is with COS is approved. These 3 days will create a any problem for me.