You have no cause for worry. The Widal test is a serological test for Salmonella typhi and S. paratyphi (A, B and C). It demonstrates salmonella antibodies against the salmonella antigens (O-somatic and H-flagellar) in the blood. The widal test has limited use in the diagnosis of typhoid fever, since it is not a very accurate method. Cultures of blood, urine and faeces are better at diagnosing enteric fever.
The antibodies detected in widal persist for quite some time after the illness and the duration varies in different individuals. They have no significance on follow-up and may cause erroneous or a false positive on testing during a subsequent febrile episode.
You can safely join your duties provided you are feeling all right and have no fever. The only precautions you need to follow are good hygienic practices, like washing your hands with soap and water after going to the toilet, since you could be excreting the bacteria in your stool for some time (as a convalescent carrier).