Does creatinine go up and down after transplant?

When my brother got diagnosed with CKD early this year, doctors suggested we get kidney transplant and my father volunteered for it. Luckily everything went well and during 4 days of stay at the hospital after transplant his creatinine came down to 1.27 but after a week it went up to 1.39. Is it concerning or does it happen in early days of transplant?