Should theory exams be repeated in case you have missed the practicals?

There is no rule that you have to again appear for the theory papers. You can apply for only practicals and attend those examinations only. Once you clear your practicals you will be declared passed and your certificate shows you have completed the course in compartmental mode and you will not be given any class even though you score higher marks. Your chances of getting admission for higher degrees will be difficult. To avoid this problem you should clear all your examinations in one go. So you have to apply for all the subjects and appear for all final year papers including theory and practical and clear them in one chance. In such a case, you will be declared passed in a class based on the percentage and you can go for further study without any problem.
This is the rule in many universities. However, I suggest you contact the University from which you appeared for the examinations. You have to contact the examination controller and get official information and then proceed accordingly.

Since you have missed your practical session in your final examination and you appeared for the theory paper only, you would be required to appear in both the parts in the next time so as to get your final results to have passed the final examination on the compartmental basis.
You have not indicated the stream which your are currently pursuing. Is it an arts stream such as Psychology or Geography or otherwise. This might be one of practical papers of the science stream.
Passing the examination in the practical mode can undertake their higher studies though it becomes difficult in other colleges to accommodate you and in your case, you can continue your studies for higher education in your existing college after the declaration of your results.
For a better scope, I would advise you to make one more attempt to appear in all the papers in the next year so as to get the final results with some class or division depending upon your performance in the next attempt. Such a degree would be acceptable in all the academic institutions apart from its acceptance in your job opportunities.

There are some subjects where practicals are also associated with it and theory part and practical part both combine to form one single subject. If you are not able to clear this subject first time either in theory or practical then you have to reappear for it fully next time. It means that you will have to reappear for theory as well as practical.
Generally such opportunity is provided to the students as a supplementary exam very near or sometimes within the same academic cycle. So you have to find out the exact schedule for that. There might be some difference in the methodology executing this supplementary exam from one institution to another and one must get clarifications for the same from the particular institution in which one is going to appear in such a supplementary exam.