[curcercanty]

you can call him and tell sorry that I told I was a non-muslim when you asked me last time as I had problem telling I was a mulsim that time. (you are not lying as you had the problem telling the truth that time and lying is indeed a problem). inshaaALlah it will go well. Sort it out soon lest it takes over your mind and keep you disturbed. Sometimes shaitans confuses and troubles us so much when things can be sorted easily inshaaAllah.
Yeah do istighfar as others suggested and keep us in your duas. Verily without Allah's help none can go any good deed nor abstain from any sin nor one can repent. The feel of guilt is the sign of eemaan. Allahu alam.