The time it takes for dissolvable or absorbable stitches to disappear can vary.
Most types should start to dissolve or fall out within a week or two, although it may be a few weeks before they disappear completely. Some may last for several months.
Ask your surgeon or the health professional treating you about the type of stitches you've been given and how long they expect it will take for them to dissolve.
If your wound has healed and your stitches are bothering you, you might want to consider making an appointment at your GP surgery to have them removed by the practice nurse, rather than waiting for them to dissolve completely.