Hello. The nature of the condition cannot be accurately determined from photographs alone, but the wounds seem to be older. Although the wound looks partially healed on the surface, it may be infested by the presence of pathogens (you can see that the tissue is moist and shows a non-specific colour in some areas). As the cambium appears to be affected to a fairly high extent (about 30-40% of the circumference, according to the photographs), the likelihood of normal development of the maple tree over time is low.
If you want to keep this ornamental tree, you may consider cleaning the dead tissue from the trunk with a sharp and disinfected tool. Afterwards, the wounds on the trunk can be treated with a copper-containing solution, e.g. , in a dose of 10 – 20 g / 1 L of water. The prepared solution can be applied with a brush. Finally, you can apply or , to close and heal the wounds faster. For more information on treating injuries to tree species, please read our article: Tree wounds and frost cracks - How do we treat them?.
As it is known that vigorous plants that benefit from optimal environmental and care conditions are rarely affected by diseases or pests, it is recommended to ensure the optimal growing conditions for ornamental trees (Maple, planting guide and care work). An adequate fertilization is also essential to ensure a healthy growth and development. To improve the quality of the soil and revitalize the roots, you can consider gently loosening the topsoil around the plant and using a fertilizer such as (by spreading it and incorporating it into the topsoil – one application at this time, as recommended in the product description).
Given the current appearance of the stem (most likely the sap is only circulating on one side of the trunk), it is not possible to say how the maple will develop in the future. In case you notice other symptoms, we are waiting for your message with photos.