Am I obligated to offer expiation for an oath after swearing not to contact someone until he initiates contact, then I went back on my word and contacted him, knowing that I am unable to feed ten needy people?

Whoever swears to do something and does not do it, or swears not to do something and does it, must offer expiation for breaking an oath (kaffarat yamin (definition)). Since you did what you swore not to do, you must offer expiation for breaking an oath, which is: feeding ten needy persons, or clothing them, or freeing a slave. If you cannot find any of these, then you must fast for three days. This is based on the Almighty's saying: "Its expiation is the feeding of ten needy people from the average of that which you feed your [own] families or clothing them or the freeing of a slave. But whoever finds not [the means to do so] - then a fast of three days. That is the expiation for oaths when you have sworn. And guard your oaths." [Al-Ma'idah:89]. Since you are unable to feed, clothe, or free a slave, you must fast for three days.