As commented, you need to use the pump to preserve penile health, but without nerves, it won't cause natural erections to return. For erections, you will need to use the penile injections, pellets, or cream. (You can use the pup with constriction rings too, but not everyone finds those erections suitable for use with sex.)
It is also worth asking for a pack of 8 x 100mg Sildenafil (Viagra). These won't work if you really have no nerves, but occasionally some nerves are spared which the surgeon didn't know about, and in that case, you might get a response from the Viagra. Try them a few times (a single failure isn't indicative of it not working), and then perhaps every few months, have another go in case there's been any recovery in that period. This probably won't work, but it's worth a go on the off-chance.
Your GP should be able to give you the Sildenafil, but you'll need an appointment with the ED clinic to be taught how to use the injections or pellets, before your GP can prescribe them.