1. Is your uncle who made the WILL alive?
2. Two persons would have witnessed the execution of the WILL, you are one and where is the other one.
3. I think it was your uncle's self acquired property and he was well within his rights to give his property to any body including his brothers and there can be no compulsion that the self-acquired property can only be given to sons and you, as one of the witnesses, had no role to play in the execution of the WILL.
4. Your uncle's sons may challenge the execution of WILL in the competent court and may not approach Police in this regard. Even if the Police come in search of you, they may come only to enquire you to know whether you had abetted in the execution of WILL by your uncle.
5.You can take the help of a local lawyer if need be.