Covid Recovery but increased sugar level

Name : Soma Gopal Age : 55 years Weight: 70 kgs Height : 5.6 feet Oxygen: 97,98,99 Pulse : 99,100,101,102,103 Temperature: Normal Other problems: BP On August 25th we have done rapid antigen test and got negative and a day after symptoms were started and done CT scanning on August 30th got CoRad 4 and admitted in hospital immediately and got treatment for a week with Remedisivir and Merependem and etc., But after 4 weeks after discharge his sugar levels were increasing continuously Fasting was 193 to 209 and post lunch was 392 to 408. And went to one diabetic specialist near by and done with ECG and X Ray and Kidney functioning test and Liver functioning test and sugar test and blood test and urine test and doctor told us everything was fine but due to raise in sugar levels its effecting on Kidneys. Heart and everything was fine and no need to worry and gave medicines and insulin twice a day 18 and 12 units. From yesterday his hand was wounded were he take insulin. is it serious?