Two accidents in two different countries - where should I claim?

I had an accident last August. (I work in the door's factory and I am a blue-collar worker) and I am staying on the medical leave till the beginning of Octoer After the ultrasonography it came out that the joint cartilage is damage and that the problem with my spine which I have already treated from the car accidente, came back. Who should shaoulder the responsibility in this case? Should i claim for the support from my employer? Should the cover for loosing of earnigs should be provided by my company or the insurance agency which gave me compensation for the car accident? I get only 3000 paunds - it's an absurd! What will be more gainful? The employer is insured in UK and the insurance for the previous accident is polish. After the work accident they took the minutes and let me go home. I was working another 3 days but the pain was really strong and I went to the doctor who denied to examinate me as I was not belonging to that medical centre. They wanted me to come back in few days to register there and only then to arrange the date of seeing the doctor. After that, I decided to go back immidiately to my country (Poland) where they helped me without any problems. So, I started the treatment in Poland but I have the rehabilitation in UK. How should I prepare before claiming? What documents will be needed in order to not loose the case?