If you suffer an injury at work, you should report it to your line manager and the safety representative at your workplace. If you are a union member, you should tell your union as well.
There are several reasons why your employer might wish to interview you. There are certain injuries and work-related illnesses that the employer must report to the Health and Safety Executive (HSE) and there might be an HSE investigation as a result. If that was the case, you would have a duty to co-operate.
You might be eligible for industrial injuries disablement benefit or compensation from your employer, depending on the circumstances. Most employers are required by law to have insurance in place against liability for injury or disease to their employees related to their work (the Employers’ Liability (Compulsory Insurance) Act 1969).
Whatever the circumstances, it would be sensible to involve your union (if you are a member) and your workplace safety representative as soon as possible, if you haven't already.