You should not defrost by using boiling water, having said that, getting impatient and using it straight away was probably the best thing you did.
Food is dangerous in that half way state - between cold and cooked. so pouring boiling water on the chicken, and then leaving it to sit half raw and half partially cooked could leave to problems.
Make sure that the chicken is fully cooked before you serve it, and it should be fine. The main problem with cooking frozen meat is that the outside is cooked, before the middle is done, and that leads to the half cooked/half raw problem. If you chopped it up and are cooking it in small pieces, you should avoid that problem, but just be careful that it is fully cooked all the way through.