ITC ON PURCHASE JUST BEFORE GETTING REGISTRATION

No, primary condition for claiming input tax credit is to be a registered taxable person.

Also, since you had no GST registration, the purchases made before getting GST registered would have been shown as B2C transaction by supplier and not B2B. 

If you have stock in hand as on date of registration then you cN claim itc by filing form ITC01...

I am in agreement with Mr. Pritesh and want to add few more points here: 1. You can take ITC in form ITC 01 only if you applied for registration within 1 month of becoming liable to register. 2. Invoice relating to goods in stock should not be older than 1 year. 3. ITC01 should be filed within 1 month from getting registration.