Using pebbles for ramy al jamarat, taken from my own country is lawful or not. If not, then what should one do who has done so.

All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His Slave and Messenger.

It is not stipulated that the pebbles should be picked up from a specific place. It is permissible for the pilgrim to throw the pebbles taken from anywhere. Ibn Al-Munthir said as it was stated in Al-Majmoo‘ by An-Nawawi: "I do not know any difference of opinion among scholars that they (the Jamaraat pebbles) will be valid from anywhere one takes them."

Ibn Muflih said in Al-Furoo‘: "One can gather seventy pebbles which are a little bigger than a chickpea from anywhere." 

Shaykh Al-Islam Ibn Taymiyyah held the same opinion in Majmoo‘ Al-Fataawa saying: "One may gather pebbles from any place."

Shaykh Ibn ‘Uthaymeen said in Sharh Al-Bukhari: "Is it stipulated that such pebbles should be from a specific place or rather they can be taken from anywhere? The Answer is: From anywhere." He also said: "Taking pebbles from Muzdalifah is not a Sunnah. One can take them from any place." 

On the other side, some jurists disliked taking pebbles from outside the sanctuary that surrounds Makkah). Al-Mawsoo‘ah Al-Fiqhiyyah reads: "Shaafi‘i scholars allowed gathering them from the road or from anywhere and said: It is disliked to gather them from outside the sanctuary because that means preferring that place to the honored sanctuary. It is also disliked to gather them from any impure place or from the pebbles that have been thrown before. Imaam Ahmad said: "Take pebbles from anywhere you wish." [End quote]

Accordingly, it is disliked to throw pebbles taken from outside  the sanctuary, whether from the country of the pilgrim or otherwise; however, if one throws them, then this will be valid and he does not have to do anything more.

Allaah Knows best.