In my opinion you can use it. A prayer rope is nothing more than a tool to help us with our prayers. It shouldn't have to matter which religion it is from.
I am Eastern Orthodox and I use the orthodox prayer rope, but in my last vacation I forgot my Prayer Rope, so I bought a Catholic Rosary and used it in my vacation for praying. I marked it with some tape after each 33rd bead (like with my Orthodox Prayer rope), to signal when to do my prostrations.
I still have it as a backup, I did ask my pastor to bless it, because that gives me a comforting feeling. When I asked him about if it is wrong he reassured my thoughts I already had, that it is just a tool to guide us in prayer, but that it is a good idea to bless it.