Can one end of a transformer be used as a choke?
Yes.

A transformer is made of (at least) two windings that are coupled together through a ferromagnetic core (iron plates). A choke/inductor uses exactly the same principle, but only has (usually) one winding. Both transformers and inductors need not to have a core - may be simply a set of wire loops (aircore). Such device is not subject to an effect called core saturation. This prevents transformers and inductors with a core from functioning properly when forced to conduct excessive amounts of current. This is probably not your case though.