A criminal record is for life. For many things, however, (such as most applications for insurance cover or for most types of employment) convictions become 'spent' after a specified period of time. The relevant time for your sentence is a period of 5 years. (The period is halved for those under 18 but the relevant age is the offender's age at the date of conviction, not at the time of the offence). Once a conviction is spent, it doesn't have to be declared when applying for employment unless the type of employment is exempted from the provisions of the Rehabilitation of Offenders Act.
Unfortunately for you, almost all jobs within the health service (and certainly all nursing jobs) are exempted from the RoO Act. This means that, as far as the health service is concerned, your conviction will never be spent.
Your conviction doesn't automatically bar you from acceptance for nursing traing. You would have to declare it if you applied (whether now or in many year's time). It would be up to those people who are responsible for the selection of candidates to decide whether or not you could be permitted to join the course. Unfortunately for you, it's unlikely that they'd be prepare to 'take the risk'. Even though your conduct on the course might be exemplary, the course tutors would be concerned about the poor publicity which might arise if one of the 'sensationalist' tabloids found out that they'd accepted someone with a conviction for violence.
Even if you could get a place on the course, you might find that you couldn't get employment. Once again, you'd have to declare the conviction and, once again, few people would be prepared to 'take a risk'.
Sorry :-(
Chris